1. Field of the Invention
The present invention relates to a printhead substrate, printhead, and printing apparatus.
2. Description of the Related Art
A printhead substrate can employ a time-divisional driving method of dividing a plurality of printing elements into a plurality of blocks and driving the printing elements for the respective blocks in order to suppress the influence of heat between adjacent printing elements. A plurality of printing elements arranged on a printhead substrate are assigned to respective groups by a predetermined number of adjacent printing elements. The “block” represents printing elements of the respective groups for which driving control is performed at the same timing.
Japanese Patent Laid-Open No. 2006-7763 discloses a structure in which a reference current circuit forming a current mirror with a current source disposed for each group is arranged. Each current source supplies, to each printing element to be driven in each group, a current corresponding to the current value of the reference current circuit in accordance with an externally input signal. The externally input signal is determined based on manufacturing variations between printhead substrates. In Japanese Patent Laid-Open No. 2006-7763, this arrangement controls the driving forces of a plurality of printing elements in accordance with manufacturing variations between printhead substrates.
If the characteristics of printing elements greatly vary on a single printhead substrate, the driving forces of the printing elements need to be controlled individually. The technique disclosed in Japanese Patent Laid-Open No. 2006-7763 is advantageous for manufacturing variations between printhead substrates, but does not consider characteristic variations between printing elements on a single printhead substrate.